1. Field of the Invention
The present invention concerns an improved method for the isolation of trinitromethyl compounds. Specifically, the present invention relates to a method for the isolation of trinitromethane (nitroform) by the addition of sulfuric acid to a nitration mixture of nitric acid, nitroform, and water, and perferentially extracting the nitroform with an organic solvent such as methylene chloride. The nitroform is then extracted from the methylene chloride into water.
Nitroform (trinitromethane) is a very valuable compound for use in the preparation of explosive and propellant ingredients, due to its high oxygen content and labile hydrogen atom, which facilitates the preparation of trinitromethyl and fluorodinitromethyl derivatives. Of particular interest, is the use of nitroform for the preparation of bis(fluorodinitroethyl) formal (FEFO) and 1,3-bis(fluorodinitroethoxy)-2,2-bis(difluoroamino) propane (SYEP). Both FEFO and SYEP are energetic plasticizers that are being utilized in advanced solid propellants. Consequently, low-cost processes for their production are required. This, of course, necessitates starting their production with low-cost nitroform.
2. Description of the Prior Art
An industrial scale facility for the production of trinitromethane based on the reaction between acetylene and nitric acid has been developed by Nitro Nobel, as shown in the article by Wetterhold, in G. A., Tetrahedron, 19, Suppl. 1, 155 (1963). The product from this nitration consists of a mixture with the nominal composition of approximately 76% HNO.sub.3 /13% Nitroform/10% H.sub.2 O. A method for the recovery of nitroform from this mixture was developed by Nitro Nobel as shown in U.S. Pat. Nos. 2,658,084 and 3,880,941.
In this procedure, the strong nitric acid is first distilled from the reaction mixture. Water is then added to the distillation bottoms and the nitroform-water azeotrope is then distilled off. This procedure, thus, involves two distillations in which nitroform is involved. Since nitroform is an energetic explosive compound with limited thermal stability, the distillation of even nitroform solutions represents a potentially hazardous operation.